The effects of radiofrequency ablation on left atrial systolic function

Kardiologia Polska
2011; 69, 2: 116–122
ISSN 0022–9032
Original article
The effects of radiofrequency ablation on
left atrial systolic function in patients with
atrioventricular nodal reentrant and
atrioventricular reentrant tachycardias
Jacek Majewski, Jacek Lelakowski, Dominik Jędrzejowski
Department of Electrocardiology, Institute of Cardiology, Jagiellonian University, Collegium Medicum, The John Paul II Hospital,
Krakow, Poland
Abstract
Background: Recurrent supraventricular arrhythmias may cause remodelling of the atria. The effects of radiofrequency (RF)
ablation of these arrhythmias on left atrial function have not been well established.
Aim: To evaluate the effects of RF ablation on left atrial systolic function in patients with atrioventricular nodal reentrant
tachycardia (AVNRT) and atrioventricular tachycardia (AVRT). Methods: The study group consisted of 70 patients (22 men), in whom successful RF ablation of slow pathway (35 patients)
or accessory pathway (35 patients) was performed. Patients with atrial fibrillation, structural heart disease, ventricular arrhythmias (> class 3 Lown), impaired left ventricular systolic function or on antiarrhythmics were excluded. All the patients had
echocardiographic study before and 6 months after ablation. Left atrial systolic function was assessed using atrial ejection
force (AEF) according to Manning’s formula (AEF = 0.5 ¥ r ¥ MA ¥ A2, r: blood density = 1.06 g/cm3, MA: mitral orifice
area [cm2], A: A wave velocity). The following left atrial dimensions were assessed: antero-posterior (LA-AP), infero-superior
(LA-IS, long axis), medio-lateral (LA-ML, short axis). The correlations between AEF and electrophysiological parameters were
analysed (VA — ventriculo-atrial conduction, VA/CL — tachycardia cycle length).
Results: The AEF increased significantly in the AVNRT group (7.78 vs 10.75 kdynes; p < 0.001) whereas it did not change
in the AVRT group (8.96 vs 9.50, NS). Left atrial dimensions decreased significantly in both groups (AVNRT group: LA-AP:
38 vs 34 mm; LA-ML: 37 vs 33 mm; LA-IS: 51 vs 45 mm; p < 0.001; AVRT group: LA-AP: 38 vs 36 mm; p < 0.01; LA-ML:
37 vs 35 mm, p < 0.001; LA-IS: 50 vs 46 mm; p < 0.001). There was a significant correlation between the increment of AEF
and electrophysiological parameters of the tachycardia (VA, r = –0.51 and VA/CL, r = –0.53).
Conclusions: 1. RF ablation of AVNRT is associated with the improvement of left atrial systolic function. 2. Left atrial size
decreases following RF ablation of both AVNRT and AVRT. 3. The effects of RF ablation on the left atrial systolic function
depends on electrophysiological parameters of the tachycardia (VA and VA/CL).
Key words: radiofrequency ablation, AVNRT, AVRT, left atrium
Kardiol Pol 2011; 69, 2: 116–122
Address for correspondence:
Jacek Majewski,, MD, PhD, Department of Electrocardiology, Institute of Cardiology, Jagiellonian University, Collegium Medicum, The John Paul II
Hospital, ul. Prądnicka, 31–202 Kraków, Poland, tel: +48 12 614 23 81, e-mail: [email protected]
Received: 06.08.2010
Accepted: 27.10.2010
Copyright © Polskie Towarzystwo Kardiologiczne
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The effects of radiofrequency ablation on left atrial systolic function
INTRODUCTION
Radiofrequency ablation (RF) is an established method of treatment of atrioventricular nodal reentrant tachycardia (AVNRT)
and atrioventricular reentrant tachycardia (AVRT) [1–3].
During AVNRT or AVRT, adverse haemodynamic changes occur, such as pulmonary artery wedge pressure elevation and cardiac index drop [4]. Recurrent attacks lead to
deterioration of left ventricular (LV) systolic function and the
development of arrhythmic cardiomyopathy [5]. It has been
demonstrated that elimination of arrhythmia by ablation can
restore normal LV function [6]. A tachycardia attack also causes an increase of atrial pressures, which are higher in case of
AVNRT than AVRT [7]. This results from differences in anatomical substrate and electrophysiological characteristics of the
two types of arrhythmia. During AVNRT, atrial contraction
occurs almost simultaneously with ventricular contraction,
when atrioventricular (AV) valves are closed. During AVRT,
the reentry loop is greater and consequently atrial contraction is delayed in relation to ventricular contraction, when
AV valves are partially open [8, 9].
In patients with paroxysmal atrial fibrillation (AF) it has
been demonstrated that recurrent arrhythmia causes remodelling of the atrial wall and can change its electrophysiological parameters such as refractoriness and dispersion of the
refractoriness [10, 11]. Prevention of AF recurrence can inhibit the remodelling process. However, current knowledge
concerning the remodelling of the atria in patients with AVNRT
and AVRT and the impact of therapy on this process is incomplete, which prompted our research.
METHODS
Patients
Patients were selected from 196 consecutive patients (72 males) treated by RF ablation in our institution. The following
inclusion criteria were adopted: 1. good immediate effect
and no complications of slow pathway RF ablation (AVNRT
subgroup) or accessory pathway (WPW subgroup); 2. no
arrhythmia recurrence at 6-month follow-up; 3. normal LV
systolic function (ejection fraction [EF] > 50%, absence of
regional wall motion abnormalities), end-diastolic LV dimension within the normal range on pre-ablation echocardiography study.
Exclusion criteria were as follows: 1. more than 1 tachycardia type as confirmed by electrophysiology study (EPS);
2. structural heart disease such as ischaemic, congenital or
valvular heart disease or cardiomyopathy diagnosed according
to standard criteria; 3. co-morbid AF as confirmed by ECG,
Holter study or induced during EPS; 4. ventricular arrhythmia of intensity exceeding Lown class 3 on 24-hour Holter
ECG; 5. antiarrhythmic drug therapy or other drug therapy
that could potentially alter the left atrial (LA) function after
ablation (rennin–angiotensin–aldosterone system blocking
agents, statins).
Finally, 70 patients were included (22 men) aged 43.9 ±
± 11.1 years (23–68); 35 patients in whom RF ablation was
performed for AVNRT and 35 patients in whom ablation was
carried out for AVRT. The subgroups did not differ significantly in terms of either mean age (45.6 years vs 42.2 years) or
sex (8 males vs 13 males, respectively).
Electrophysiology study and RF ablation
The procedure was performed after obtaining written, informed consent from all participants. Quadripolar diagnostic
electrodes were introduced via the right femoral vein and
positioned in the right ventricular apex, high right atrium and
in para-hisian area. Through left subclavian vein, decapolar
electrode was introduced into coronary sinus.
Full programmed pacing protocol of the ventricles and
the atria was performed, aiming at induction of the arrhythmia. The type of arrhythmia was diagnosed based on the commonly adopted criteria [1]. After study completion, RF ablation of the arrhythmia substrate was performed. In all 35 of
the AVNRT patients, slow pathway ablation was performed
using an electro-anatomical method [12, 13]. The procedure
was successful if no AVNRT or no more than one reciprocating impulse (“echo”) were induced during pacing in basic
conditions and after intravenous orciprenaline administration.
In the WPW subgroup, ablation of the overt accessory
pathway (AP) (i.e. with antegrade conduction) was performed
during sinus rhythm. Concealed pathways (conducting only
retrogradely) were mapped during ventricular pacing or during AVRT, in search for a site of the earliest retrograde atrial
activation [14]. Ablation of the right-sided AP was done via
the right atrium, after introducing the electrode via the right
femoral vein. Left-sided pathways were eliminated via the LA,
by trans-septal puncture. The procedure was successful when
AP conduction was fully blocked and when no tachycardia
could be induced. The AP localisation in the study group is
presented in Table 1. Five of the left-sided lateral pathways
were concealed. In all patients, only orthodromic AVRTs were
induced.
The following parameters were analysed: 1. ventriculoatrial coupling (VA) during arrhythmia — measured as the
interval between local right ventricular activation to local high
right atrial activation; 2. tachycardia cycle length (CL) measu-
Table 1. Localisation of accessory pathways in WPW patients
Left-sided lateral 17 (48%)
Left-sided postero-septal
5 (14%)
Right-sided postero-septal
8 (23%)
Right-sided antero-septal
2 (6%)
Right-sided mid-septal
1 (3%)
Right-sided lateral
2 (6%)
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Jacek Majewski et al.
Table 2. Left atrial dimensions and atrial ejection force (AEF) before ablation and 6 weeks post-procedurally
Parameter
Before ablation
After ablation
P
LA-AP [mm]
38 ± 3
34 ± 2.9
0.001
LA-ML [mm]
37 ± 3.6
33 ± 3.4
0.001
LA-IS [mm]
51 ± 4.1
45 ± 5.2
0.001
AEF [kdyn]
7.78 ± 2.87
10.75 ± 3.76
0.001
LA-AP [mm]
38 ± 3
36.5 ± 3.1
0.01
LA-ML [mm]
37 ± 2.8
35 ± 3.4
0.001
AVNRT group:
WPW group:
LA-IS [mm]
50 ± 3
46 ± 3.9
0.001
AEF [kdyn]
8.96 ± 2.65
9.50 ± 3.58
NS
AVNRT — atrioventricular nodal reentrant tachycardias; WPW — accessory pathway; rest abbreviations: see “Methods”
red as RR interval on surface ECG; 3. the VA/CL ratio; 4. the
number of RF applications.
In all patients before ablation and at 6 months post-procedurally, history was taken and physical examination performed, along with standard surface ECG recording, 24-hour
Holter ECG and echocardiographic study.
Echocardiography
The study was performed using Sonos 1000 Hewlett-Packard
machine with a 2.5/3.5 MHz transducer and included
M-mode, two-dimensional (2D) and Doppler examinations,
with patient in supine left-lateral position. Simultaneous lead II
surface ECG recording was obtained. Cardiac chamber sizes
were measured by M-mode, in parasternal long axis view,
under control of 2D imaging. Left atrial size was also assessed
in the apical 4-chamber (4CH) view in end-systole. All measurements were performed during sinus rhythm of less than
80 bpm.
Mitral valve area was assessed based on mitral annulus
measurement in apical 4CH view. The following parameters
were assessed; 1. antero-posterior LA dimension (LA-AP) in
parasternal long axis view; 2. inferior-superior LA dimension
(LA-IS, long axis) in the apical 4CH view; 3. medio-lateral
(LA-ML, short axis) in the apical 4CH view; 4. mitral valve
area (MA); 5. peak atrial wave velocity of the LV inflow (A);
6. LA ejection force (AEF), calculated by Manning formula [15]:
AEF = 0.5 ¥ r ¥ MA ¥ A2, where r — blood density index =
= 1.06 g/cm3, MA — mitral valve area [cm2], A — peak velocity of the mitral inflow A wave.
Statistical analysis
Measurements are presented as mean values ± SD and
ranges or numbers and percentages. Numerical data were
compared by Student t test and within groups, the formula
for paired data was used. Non-parametric data were compared with use of c2 test. Correlations were tested by Pear-
son correlation coefficient. Significance level was set at
p < 0.05.
RESULTS
Electrophysiological parameters
The VA time in the entire group was 107.1 ± 57.6 ms
(25–225 ms). It was significantly shorter in the AVNRT subgroup (53.7 ± 17.5 ms; 25–90 ms) in comparison with the
WPW subgroup (160.6 ± 23.6 ms; 125–225 ms; p < 0.001).
Tachycardia CL did not differ significantly between subgroups (340.3 ± 52.4 ms vs 350.1 ± 46 ms, respectively).
The VA/CL ratio was significantly lower in the AVNRT subgroup (0.2 ± 0.1) in comparison with the WPW subgroup
(0.5 ± 0.1; p < 0.001). The number of RF applications was
similar in both groups (8.6 ± 7.6 vs 9.2 ± 7.6; NS).
Echocardiographic parameters
In the AVNRT subgroup, a significant reduction of the LA size
and significant AEF increase were noted (Table 2). In the WPW
subgroup, a significant reduction of LA size was also noted
but AEF was not significantly altered after ablation. The reduction of LA size and AEF change were significantly greater
in the AVNRT subgroup (Table 3). In the entire study group,
a negative correlation was found between AEF increment
(DAEF) and VA time, (r = –0.51) and VA/CL ratio (Figs. 1, 2).
The number of RF applications had no impact on the studied
parameters.
DISCUSSION
The improvement of the LA systolic function and LA size reduction after RF ablation have been well demonstrated in
patients with AF or atrial flutter [16, 17]. However, current
knowledge concerning treatment of reentrant tachycardias
of AVNRT or AVRT type on LA systolic function and remodelling is incomplete. This issue was a matter of only a few
studies. Left atrial size reduction was reported after AVNRT
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The effects of radiofrequency ablation on left atrial systolic function
Table 3. Comparison of changes (D) of left atrial size and atrial ejection force (AEF) in both groups after ablation
Parameter
AVNRT group
WPW group
P
DLA-AP [mm]
–3.7
–1.5
< 0.05
DLA-ML [mm]
–3.6
–2.4
< 0.05
DLA-IS [mm]
–6.0
–4.2
< 0.05
DAEF [kdyn]
2.97
0.54
0.001
Abbreviation as in Table 2.
Figure 1
1. Correlation between atrial ejection force increment
(DAEF) and ventriculo-atrial conduction (VA) time during
arrhythmia in the study group
Figure 2
2. Correlation between atrial ejection force increment
(DAEF) and tachycardia cycle length (VA/CL) ratio in the study
group
and AVRT ablation [18], however, in the literature to date,
there is a lack of data concerning the impact of ablation on
the LA systolic function.
In the present study LA systolic function was assessed by
AEF, which was introduced by Manning et al. [15]. The AEF
value is calculated based on mitral inflow data acquired during echocardiographic study, included in a formula based
on Newton’s second law of dynamics. It is believed that AEF
is a more sound index of LA systolic function compared to
peak A wave velocity of the mitral inflow.
So far the AEF measurements were used chiefly for the
assessment of atrial mechanics following AF cardioversion.
Mattioli et al. [19] carried out a prospective observation in
which AEF increased within 3 months of sinus rhythm restoration. Manning et al. [15] demonstrated that after successful
AF cardioversion, AEF increased gradually only in those patients in whom no AF recurrence was observed. It has been
assumed that AEF increase results from reversal of adverse
effects of electromechanical remodelling of the atria.
Clinical utility of AEF is not limited to atrial systolic function assessment. In patients with sick sinus syndrome (SSS) it
was demonstrated that lower AEF values are an independent
risk factor of stroke [20]. Tokushima et al. [21] observed more
frequent AF occurrence in patients with SSS and decreased
AEF. Increased AEF was in turn observed in patients with hypertrophic cardiomyopathy with the LV outflow tract obstruction [22], and in patients with chronic heart failure [23].
In the present study, a significant increase of AEF function was noted after AVNRT ablation, accompanied by LA
size reduction. The elimination of AVRT, however, caused
LA size reduction without impact on LA systolic function. The
LA size reduction was significantly greater in the AVNRT subgroup. Currently there are no commonly adopted normal
values of the AEF, against which our results could be evaluated. It is known that age is one of the factors potentially influencing the AEF values. The AVNRT and AVRT subgroups
were comparable in terms of patients’ age, hence post-procedural changes of this parameter could not have been in-
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Jacek Majewski et al.
fluenced by this factor. In studies by Manning et al. [15], the
mean value of AEF in healthy volunteers was 16.3 kdynes.
The present study lacks a control group, to which AEF
values measured in the study group could have been compared. However, AEF assessment was carried out in the same
patient before and after ablation, which allowed for assessment of changes of the parameter resulting from the procedure. In our study group, low AEF values were noted preprocedurally. These values were significantly improved only
in the AVNRT subgroup, reaching values comparable to the
results obtained by Mattioli et al. [19] in the group of patients
after electrical cardioversion.
Our results demonstrate that AVNRT exerts a more unfavourable effect on the LA function in comparison with AVRT.
This can be explained by different electrophysiological characteristics and different anatomical structure of the reentry
loop, as reflected by shorter VA and lower VA/CL value in the
AVNRT subgroup. Recurring AVNRT attacks cause a greater
pressure increase in the atria accompanied by stronger atrial
wall distension. This leads to more advanced remodelling and
greater systolic function impairment when compared to AVRT
patients. Hence, elimination of AVNRT brings about greater
improvement in terms of LA systolic function and leads to
greater LA size reduction, what was confirmed by the negative correlation between post-procedural AEF increase and VA
time during tachycardia as well as VA/CL values.
In a proportion of AVNRT and AVRT patients, paroxysmal AF can occur [24, 25]. In our study, AF occurrence was
one of the exclusion criteria. The relationship between AF,
haemodynamic remodelling and electrophysiological parameters in AVNRT and AVRT patients was studied by other
authors. Kalarus et al. [26] evaluated LA pressures during AVRT
in patients with WPW. They showed that repeated atrial wall
distension, secondary to pressure overload during AVRT, plays
a significant role in the development of atrial cardiomyopathy, which promotes AF occurrence. These authors also demonstrated, that electrophysiological parameters of the tachycardia, with special emphasis on atrial and ventricular activation temporal sequence, are important factors of AF occurrence in WPW patients. During AVRT, in patients with AF,
ventricular activation occurs markedly earlier and atrial activation markedly later than in patients without AF. It was also demonstrated that in AVNRT patients, inter-atrial conduction
abnormalities and alterations of refraction promote AF [27].
CONCLUSIONS
1. Ablation of AVNRT improves LA function, whereas AVRT
ablation does not exert such an effect.
2. After AVNRT ablation, LA size reduction was demonstrated and was significantly greater than after AVRT ablation.
3. The impact of ablation on the LA systolic function depends on electrophysiological parameters of the tachycardia (VA and VA/CL).
Conflict of interest: none declared
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Wpływ ablacji prądem o wysokiej częstotliwości
na czynność skurczową lewego przedsionka
u chorych z nawrotnymi częstoskurczami
węzłowymi i przedsionkowo−komorowymi
Jacek Majewski, Jacek Lelakowski, Dominik Jędrzejowski
Klinika Elektrokardiologii, Instytut Kardiologii, Uniwersytet Jagielloński, Collegium Medicum, Szpital im. Jana Pawła II, Kraków
Streszczenie
Wstęp: Odmienne podłoże anatomiczne i charakterystyka elektrofizjologiczna częstoskurczu węzłowego (AVNRT) i przedsionkowo-komorowego (AVRT) są odpowiedzialne za różnice hemodynamiczne między tymi dwoma typami częstoskurczów nawrotnych. Podczas AVNRT ciśnienie w przedsionkach wzrasta w większym stopniu niż w trakcie AVRT. Wpływ obu
typów częstoskurczu na remodeling i funkcję lewego przedsionka (LA) nie jest dobrze poznany. Brakuje danych na temat
wpływu ablacji AVNRT i AVRT na czynność skurczową LA.
Cel: Celem pracy była ocena wpływu leczenia AVNRT i AVRT na czynność skurczową LA.
Metody: Badana grupa obejmowała 70 pacjentów (22 mężczyzn, 48 kobiet) w wieku śr. 43,9 roku, u których wykonano
skuteczną ablację AVNRT (35 osób, podgrupa I) lub AVRT (35 osób, podgrupa II). Kryteriami wyłączenia z badań były: współistniejące choroby układu sercowo-naczyniowego, schorzenia przewlekłe, upośledzona funkcja skurczowa lewej komory, migotanie przedsionków, arytmie komorowe (> klasa III wg Lowna), stosowanie leków antyarytmicznych po ablacji. Analizie poddano
następujące parametry z inwazyjnego badania elektrofizjologicznego i ablacji RF: czas sprzężenia komorowo-przedsionkowego
(VA) podczas częstoskurczu, długość cyklu częstoskurczu (CL), stosunek VA/CL, liczbę wykonanych aplikacji RF. U wszystkich
osób przed ablacją, a następnie po 6 miesiącach od zabiegu wykonano następujące badania: wywiad i badanie przedmiotowe,
standardowe powierzchniowe EKG, 24-godzinne EKG metodą Holtera, przezklatkowe badanie echokardiograficzne. Oceniano: wymiar przednio-tylny LA (LA-AP) w projekcji przymostkowej w osi długiej, wymiar dolno-górny (oś długa) LA (LA-IS) oraz
wymiar boczno-przyśrodkowy (oś krótka) LA (LA-ML) w projekcji koniuszkowej 4-jamowej. Funkcję skurczową LA oceniano na
podstawie siły wyrzutowej LA, obliczanej wg wzoru Manninga: AEF = 0,5 ¥ r ¥ MA ¥ A2, gdzie: r: współczynnik gęstości krwi
= 1,06 g/cm3, MA: pole powierzchni ujścia mitralnego [cm2], A: maksymalna prędkość fali A napływu mitralnego.
Wyniki: Czas VA w całej badanej grupie wynosił śr. 107,1 ± 57,6 ms (25–225 ms). Był on znamiennie krótszy w podgrupie I
(śr. 53,7 ± 17,5 ms; 25–90 ms) w porównaniu z podgrupą II (160,6 ± 23,6 ms;125–225 ms), p < 0,001; CL wynosiła śr. 345,2 ±
± 49,2 ms (255–500 ms) i nie różniła się znamiennie między podgrupami I (śr. 340,3 ± 52,4 ms; 275–435 ms) i II (350,1 ± 46 ms;
255–500 ms). Stosunek VA/CL wynosił śr. 0,3 ± 0,2 (0,06–0,66). Wartość VA/CL była znamiennie niższa w podgrupie I (śr. 0,2 ±
± 0,1; 0,06–0,31) w porównaniu z podgrupą II (śr. 0,5 ± 0,1; 0,31–0,66); p < 0,001. Liczba aplikacji RF w całej badanej grupie
wynosiła śr. 8,9 ± 7,6 (1–35). W podgrupie I wykonano śr. 8,6 ± 7,6 (1–33) aplikacji RF, a w podgrupie II śr. 9,2 ± 7,6 (1–35)
aplikacji, p = NS. W podgrupie I stwierdzono istotne zmniejszenie wymiarów LA (LA-AP: 38 ± 3 v. 34 ± 2,9 mm, LA-ML:
37 ± 3,6 v. 33 ± 3,4 mm, LA-IS: 51 ± 4,1 v. 45 ± 5,2 mm; p < 0,001) oraz przyrost AEF (7,78 ± 2,87 v. 10,75 ± 3,76 kdyn;
p < 0,001). W podgrupie II również obserwowano redukcję wielkości LA (LA-AP: 38 ± 3 v. 36,5 ± 3,1 mm; p < 0,01, LA-ML:
37 ± 2.8 v. 35 ± 3,4 mm, p < 0,001, LA-IS: 50 ± 3 v. 46 ± 3,9 mm; p < 0,001), jednak AEF nie uległa istotnej zmianie po
ablacji (8,96 ± 2,65 v. 9,50 ± 3,58 kdyn; p = NS). Wymiary LA znamiennie się zmniejszyły w podgrupie I (p < 0,05). Różnica
między podgrupami w zakresie zmiany AEF po ablacji była istotna (p < 0,001). W całej badanej grupie wykazano ujemną
korelację między przyrostem siły wyrzutowej LA (DAEF) a czasem VA (r = –0,51). Stwierdzono również ujemną korelację
między DAEF a stosunkiem VA/CL (r = –0,53). Liczba aplikacji RF nie wpływała na badane parametry.
Wnioski: 1. Ablacja AVNRT powoduje poprawę czynności skurczowej LA. 2. Ablacja AVRT nie wpływa istotnie na funkcję
skurczową LA. 3. Po ablacji AVNRT wykazano zmniejszenie wymiarów LA istotnie większe niż po ablacji AVRT. 4. Wpływ
ablacji na funkcję skurczową LA zależy od parametrów elektrofizjologicznych częstoskurczu (VA i VA/CL).
Słowa kluczowe: ablacja RF, AVNRT, AVRT, lewy przedsionek
Kardiol Pol 2011; 69, 2: 116–122
Adres do korespondencji:
dr n. med. Jacek Majewski, Klinika Elektrokardiologii, Uniwersytet Jagielloński, Collegium Medicum, Szpital im. Jana Pawła II, ul. Prądnicka, 31–202 Kraków,
tel: +48 12 614 23 81,e-mail: [email protected]
Praca wpłynęła: 06.08.2010 r.
Zaakceptowana do druku: 27.10.2010 r.
www.kardiologiapolska.pl